replace petstore_api with packageName (#4921)

Author: wing328

modules/openapi-generator/src/main/resources/python/setup_cfg.mustache

@@ -5,7 +5,7 @@ verbosity=2
 randomize=true
 exe=true
 with-coverage=true
-cover-package=petstore_api
+cover-package={{{packageName}}}
 cover-erase=true
 
 {{/useNose}}